Three different wood-rotting fungi, Antrodia sinuosa , Coniophora eremophila and a species of Nodulisporium , cause heartwood rot in living lemon trees in southwestern Arizona . Earlier research demonstrated that these fungi are most active on lemon trees during the high temperatures prevalent in this region during the summer. A long-term study is now in progress to evaluate possible differences in wood rot development due to lemon tree age, lemon tree cultivar and rootstock.